In a healthy heart, blood that returns from the body to the right atrium is low in oxygen. This blood passes through the right ventricle to the lungs to be enriched with oxygen. The oxygen-rich blood returns to the left atrium, and then to the left ventricle. It is then pumped out to the body through the aorta, a large blood vessel that carries the blood to smaller blood vessels in the body. The right atrium and the left atrium are separated by a thin wall, called the atrial septum.
An atrial septal defect (ASD), i.e., a hole in the atrial septum, is a congenital heart defect. A patent foramen ovale (PFO) is also a congenital heart defect in the septum between the two atria of the heart. In PFO, the defect is a flap or a valve-like opening in the atrial septal wall.
The presence of a large ASD or PFO may result in a left-to-right shunt, which allows blood to flow from the left atrium to the right atrium. This extra blood from the left atrium may cause a volume overload in both the right atrium and the right ventricle. Left untreated, this condition can result in enlargement of the right side of the heart and ultimately heart failure.
Congestive heart failure (CHF) is a condition afflicting millions of people worldwide. CHF resulting from a weakening or stiffening of the heart muscle most commonly is caused by myocardial ischemia (due to, e.g., myocardial infarction) or cardiomyopathy (e.g., myocarditis, amyloidosis). CHF causes a reduced cardiac output and inadequate blood to meet the needs of the body.
CHF is generally classified into systolic heart failure (SHF) or diastolic heart failure (DHF). In SHF, the pumping action of a heart is reduced or weakened. A normal ejection fraction (EF), which is a function of the volume of blood ejected out of the left ventricle (stroke volume) divided by the maximum volume remaining in the left ventricle at the end of the diastole or relaxation phase, is greater than 50%. In a systolic heart failure, the EF is decreased to less than 50%. A patient with SHF may have an enlarged left ventricle because of cardiac remodeling developed to maintain an adequate stroke-volume. This pathophysiological phenomenon is often associated with increased atrial pressure and left ventricular filling pressure.
DHF is a heart failure often without any major valve disease or any impediment to the systolic function of the left ventricle. Generally, DHF is the failure of the ventricle to adequately relax and expand, resulting in a decrease in the stroke volume of the heart. There are very few treatment options for patients suffering from DHF. DHF afflicts between 30% and 70% of CHF patients.
Cardiac implants in the atrial septum have been used for many purposes. For example, septal occluders can be used for transcatheter closure of congenital heart defects, such as the atrial septal defects or the patent foramen ovale; and atrial shunt devices can be used to treat congestive heart failures by allowing a small volume of blood to travel from the left side of the heart to the right side of the heart, thereby reducing the left atrial pressure.
Most percutaneous deployment of a cardiac implant in the atrial septum is conducted through a standard right heart catheterization procedure. In such a procedure, a cardiac implant is delivered through the femoral vein, to the inferior vena cava and, to the right atrium. As shown in FIG. 1, as a delivery system enters the right atrium, it extends toward the atrial septum in an acute angle “θ”. Most cardiac implants, as being deployed from the delivery system, are generally at a right angle to the longitudinal axis of the delivery system. Thus, when the implant is being deployed at the atrial septum but before released from the delivery system, the implant deployment position can be distorted by the strain imposed by the delivery system to the atrial septum. In such an event, when a clinician releases the implant, and as the distorted septum resumes its natural state, the implant deployment position can change in the process. In certain instances, the released implant can be improperly deployed and must be retrieved to prevent embolization. Thus, there is a need for a clinician to assess the “true” deployment status of the cardiac implant, i.e., how the implant is positioned in its released state, while still maintaining contact with the implant. In the event that the implant is not successfully deployed, the clinician can recapture the implant by using the implant retention mechanism or an implant retrieval mechanism.